指定的强制转换无效铸造的int字节

Question

我有一个名为实体：它有一个属性ShowDuringRegistration为字节

与执行此行中我总是看到这个错误AttachmentType：指定强制转换无效,,不管那我发送一个字节作为参数

Repository<AttachmentType>.FindBySpecification(new AttachmentSearchSpecification() 
    .WithTraceCodeOrNationalNumber(traceCodeString) 
    .WithAttachmentTypeShowDuringRegistration(false)) 
    .Select(p=>new attachmentTypeModel() 
    { 
     Id=p.Id, 
     Title=p.Title 
    }) 
    .ToList(); 

public AttachmentSearchSpecification WithAttachmentTypeShowDuringRegistration(bool showDuringRegistration=false) 
{   
     AddExpression(p => p.AttachmentType.ShowDuringRegistration == (showDuringRegistration ? 1 : 0)); 
     return this; 
} 

即使我一个字节发送给WithAttachmentTypeShowDuringRegistration方法，并比较与财产ShowDuringRegistration它不工作

byte b=0; 
Repository<AttachmentType>.FindBySpecification(new AttachmentSearchSpecification() 
    .WithTraceCodeOrNationalNumber(traceCodeString) 
    .WithAttachmentTypeShowDuringRegistration(b)) 
    .Select(p=> new attachmentTypeModel() 
    { 
     Id=p.Id, 
     Title=p.Title 
    }) 
    .ToList(); 

public AttachmentSearchSpecification WithAttachmentTypeShowDuringRegistration(byte showDuringRegistration) 
{ 
    AddExpression(p => p.AttachmentType.ShowDuringRegistration == showDuringRegistration) 
    return this; 
} 

这里是当误差提出：

select cast(count(*) as INT) 
as col_0_0_ from EmploymentRegistration.[Attachment] 
attachment0_, EmploymentRegistration.[Demand] demand1_, 
EmploymentRegistration.[AttachmentType] attachment5_ where ttachment0_.DemandId=demand1_.DemandId 
and demand1_.PersonId=person3_.PartyId and person3_.PartyId=birthcerti4_.PersonId and 
attachment0_.AttachmentTypeId=attachment5_.AttachmentTypeId 
and (demand1_.TraceCode like ('%'+?+'%') or birthcerti4_.NationalNumber like ('%'+?+'%')) 
and attachment5_.ShowDuringRegistration=? 

内部异常：{"Specified cast is not valid."}

protected void AddExpression(Expression<Func<T, bool>> expression); this method get an experssion and append that expression to the linq query 



public class AttachmentTypeMap : ClassMap<AttachmentType> 
{ 
    public AttachmentTypeMap() 
    { 
     Schema("EmploymentRegistration"); 

     Id(p => p.Id);//int identity 

     Map(p => p.Title);//string 

     Map(p => p.ShowDuringRegistration);//byte 

     Map(p => p.ScriptName) 
      .Length(100); 

     References(p => p.EmploymentLicense); 
    } 
}` 

通过执行这样一个简单的查询：

Repository<AttachmentType>.FindAll().Where(p=>p.ShowDuringRegistration==(byte)1).Tolist(); 

，将这样 生成从 EmploymentRegistration中选择cast（count（*）as INT）col_0_0_ [AttachmentTyp e] attachment0_左外连接 EmploymentRegistration。 [EmploymentLicense] employment1_ on attachment0_.EmploymentLicenseId = employment1_.EmploymentLicenseId其中
attachment0_.ShowDuringRegistration =？

当我想通过

int _totalItems = Query.Count(); //Query is IQueryable<T> 

知道返回值的数目，我会看到错误再次

甚至只是执行这个查询的错误会提高酷似前：

//ShowDuringRegistration is byte? 
var data= Repository<AttachmentType>.Find(p => p.ShowDuringRegistration == 0) 
            .ToList(); 
public interface IRepository<T> where T : class 
{ 

    IQueryable<T> Find(); 

    IQueryable<T> Find(object id); 

    IQueryable<T> FindBySpecification(ISpecification<T> specification); 

    IQueryable<T> Find(Expression<Func<T, bool>> expression); 

} 


public static class Repository<T> where T : class 
{ 

private static IRepository<T> Current 
    { 
     get { return UnitOfWork.GetRepository<T>(); } 
    } 

public static IQueryable<T> Find(Expression<Func<T, bool>> expression) 
    { 
     return Current.Find(expression); 
    } 

public static IList<T> FindAll(Expression<Func<T, bool>> expression) 
    { 
     return Current.FindAll(expression); 
    } 

} 

Answer 1

你实际上并没有使用一个字节 - 你正在使用一个int。它通常用C＃工作，因为ShowDuringRegistration将被提升为int，然后进行比较。试试这个：

public AttachmentSearchSpecification WithAttachmentTypeShowDuringRegistration 
    (bool showDuringRegistration=false) 
{ 
    byte value = showDuringRegistration ? (byte) 1 : (byte) 0; 

    AddExpression(p => p.AttachmentType.ShowDuringRegistration == value); 
    return this; 
}